This invention relates generally to the field of plastics blends or blends of polyolefin plastics with other plastics and elastomers and, optionally, thermal and environmental stabilizers, process aids, fillers, etc. Specifically, it is directed to blends of polyolefin plastics such as polypropylene, polypropylene reactor copolymer, polybutylene, low density polyethylene, linear low density polyethylene, and high density polyethylene with a polyisobutylene-backbone elastomer component such as polyisobutylene, butyl rubber and halogenated butyl rubber, and a copolymer component of ethylene and an unsaturated ester of a lower carboxylic acid. The compositions comprising these essential blend components can optionally contain process aids, antiblock additives, thermal and environmental stabilizers, such as antioxidants, antiozonants, U.V. stabilizers, etc., fillers, extenders, pigments, foaming agents, etc. The final compositions are useful in the production of films, filaments, rods, molded and extruded shaped articles.
Isobutylene-backbone elastomers, for example, polyisobutylene elastomers, are commonly used in industry to modify polyolefins for improvement in low temperature properties, impact strength, toughness, tear resistance and flexibility; concentrations are typically in the range of 10 to 40 weight percent polyisobutylene. As the elastomer concentration is increased the benefits of the rubber are more apparent, however, the melt viscosity of the polymer blend is increased to such an extent that high pressures and uneconomically low throughput rates result.
Limited teachings are available in the prior art which disclose various plastics blend compositions, but individually and collectively they fail to provide the advance which is disclosed by the inventor herein:
U.S. Pat. No. 4,311,808 to Su relates to a composition comprised of: polyisobutylene, an ethylenepropylene copolymer, and ethylene vinyl acetate copolymer (EVA). The EVA copolymer contains up to 20% vinyl acetate. The composition may be used for forming films. PA1 Japanese Pat. No. 73,740 discloses a polymeric composition comprised of EVA, ethylene-.alpha.-olefin copolymer, and a polyolefin such as crystalline polypropylene, high density polyethylene and polybutene-1. PA1 (a) from about 20 to about 65 weight percent of the polyolefin component, preferably from about 25 to about 60 weight percent, more preferably from about 35 to about 55 weight percent; PA1 (b) from about 20 to about 60 weight percent isobutylene-backbone elastomer, preferably from about 25 to about 55 weight percent, most preferably from about 30 to about 50 weight percent; and PA1 (c) from about 7 to about 40 weight percent ethylene copolymer, preferably from about 10 to about 35 weight percent, most preferably from about 13 to about 25 weight percent.
Japanese Pat. No. 48,233 relates to a complex process for producing a hot melt sealant which, at one stage involves a polymeric composition comprised of EVA, polyisobutylene, or ethylene-propylene copolymer.
A German Pat., No. 2,844,363 discloses a polymeric blend of low density polyethylene and/or EVA, ethylene-.alpha.-olefin copolymer, and a polyolefin such as crystalline polypropylene, high density polyethylene, and/or polybutene-1. Such a blend is used in the manufacturing of shrink film. This patent is based on an original Japanese disclosure and is also available as three related U.S. Pat. Nos.: 4,336,212; 4,302,557 and 4,277,578 to Yoshimura et al.
The United States patent to Decroix, U.S. Pat. No. 4,126,649, relates to a polymeric composition comprised of: EVA and polybutene-1 or butene-ethylene copolymer.
A patent to Ticknor, U.S. Pat. No. 4,189,519, relates to a resin blend of EVA and polybutylene (polybutene-1) applied to a substrate of high density polyethylene or nylon.
U.S. patent application Ser. No. 362,103 discloses blends of polyolefin plastics with elastomeric plasticizers. The elastomeric plasticizer comprises polyethylene or a copolymer of ethylene and an unsaturated ester of a lower carboxylic acid, olefinic elastomer and hydrocarbon oil. The use of the elastomeric plasticizer is shown to be advantageous in handling and processing the compositions and in achieving good dispersion of the ingredients useful for the preparation of film.